1. Field of the Invention
The present invention generally relates to an optical film and a back light module, and more particularly, to an optical film unlikely scraped and a back light module using the optical film.
2. Description of Related Art
FIG. 1 is a diagram of a conventional backlight module. Referring to FIG. 1, a backlight module 100 includes a set of light sources 110, a reflective plate 120, a light guide plate (LGP) 130 and a plurality of optical films 140. The LGP 130 has a light incidence surface 132 and a light-emitting surface 134 connecting the light incidence surface 132. The set of light sources 110 is disposed beside the light incidence surface 132 of the LGP 130, and the optical films 140 are disposed over the light-emitting surface 134. Besides, the LGP 130 is sandwiched between the reflective plate 120 and the optical films 140.
In fact, the light emitted by the set of light sources 110 is reflected by the reflective plate 120 and then passes through the LGP 130 so as to provide a planar light source for the LCD to display. The employed optical films 140 are used to further promote the light-emitting effect and the light usage efficiency of the backlight module 100. A common optical film 140 basically includes a diffuser and two brightness-enhancing films as a combination. The optical film 140 having a prism structure is usually served as a brightness-enhancing film, wherein the prism structure is suitable to concentrate the light emitted from the set of light sources 110 for increasing the light-emitting luminance of the backlight module 100 effectively. In this way, the optical films 140 enable the backlight module 100 to have higher light usage efficiency and reduced power consumption.
However, when applying a backlight module 100 in a portable information product, the sharp protrusion portions of the prism structure may be unexpectedly worn by friction and get passivated. Additionally, the sharp protrusion portions of the prism structure may also scrap other films or elements. Thus, the optical effect of the optical films 140 gets deteriorated and the backlight module 100 is accordingly unable to remain in the optimum light-emitting state as well.